But men may not get the same benefit, according to another study. Both studies were presented this week at the American Thoracic Society international conference in New Orleans.

The risk reduction for women on vitamin E supplements was equal in people who smoked -- the primary risk factor for getting COPD -- and people who didn't, says Anne Hermetet Agler, a PhD candidate at Cornell University and lead author of the study involving women.

''We saw a 10% reduction in risk," she says. The women took 600 IU of vitamin E every other day. Of the effect, she says, "It is limited to just women."

Vitamin E, an antioxidant, has been looked at as a lung disease preventive because it is thought to protect against free radicals, molecules that damage cells and one of the proposed processes by which lung disease is thought to develop. But previous research has found little or no effects of antioxidants on lung outcomes, Agler says. And other research has found increasing vitamin E may slightly increase lung cancer risk and other ill effects.